1. Field of the Description
The present description relates, in general, to three dimensional (3D) or volumetric displays adapted to provide the illusion that a virtual or projected image is a 3D image or has volume. More particularly, the description relates to systems and methods involving a transparent display with a dynamic mask to produce sharp 3D volumetric images or objects without requiring viewers to wear 3D glasses or the like and without (or with reduced) blow-by being transmitted through the scrim onto background props and surfaces.
2. Relevant Background
There is a growing trend toward using 3D projection techniques in theatres and amusement parks and in home entertainment systems including video games and computer-based displays. In many conventional 3D projection techniques, the right eye and the left eye images are delivered separately to display the same scene or images from separate perspectives so that a viewer sees a three dimensional composite, e.g., certain characters or objects appear nearer than the screen and other appear farther away than the screen. However, stereoscopy, stereoscopic imaging, 3D imaging, and 3D or volumetric displays are labels for any technique capable of creating the illusion of depth in an image.
Often, the illusion of depth in a photograph, movie, or other two-dimensional image is created by presenting a slightly different image to each eye or the creation of parallax. In most animated 3D projection systems, depth perception in the brain is achieved by providing two different images to the viewer's eyes representing two perspectives of the same object with a minor deviation similar to the perspectives that both eyes naturally receive in binocular vision.
There is a continuous desire and need to provide new techniques that provide cost effective but eye-catching content with depth and dimension. For example, it is desirable to grab the attention of crowds in shopping malls, on busy streets, in amusement parks, and other crowded facilities such as airports and entertainment arenas. As discussed above, 3D imagery and volumetric displays are exciting ways to appeal to viewers and hold their attention. However, the use of 3D imagery has, in the past, been limited by a number of issues. Typically, 3D projection technologies require the viewer to wear special viewing glasses. This is often inconvenient for many applications and can significantly add to costs to provide the 3D media for projection and also for the special eyewear that has to be provided to the viewer.
Some attempts have been made in providing volumetric displays without the need for eyewear, but each has its own limitations. For example, displays providing a scrim projection or traditional Pepper's Ghost illusion are common tools used throughout amusement parks and other settings. These displays allow placement of a virtual character or object (i.e., a ghost, a video of a character, or the like) within a real world scene. A scrim projection is usually accomplished by using a projection onto a scrim (e.g., an open weave material appearing transparent when lit from behind but providing a projection surface when lit from the front or viewer's side) while a Pepper's Ghost is a reflection of a display in a beam splitter. Unlike directly viewing an opaque monitor, the scrim and the beam splitter are partially transparent to the viewer (even when lit from the front) so the displayed character is not framed by the display. The virtual character can be placed relatively seamlessly behind real world objects or props (foreground elements) and in front of real world objects or props (background surfaces and elements).
Unfortunately, the partial transparency of the scrim or the beam splitter also leads to the virtual character having low contrast and being semi-transparent. This can lead to a brightly lit background surface or prop being seen through the character/object displayed on the scrim or the beam splitter, and this is especially problematic in portions of the displayed character/object that should appear dark and/or solid. The character's darkest dark portion is defined by the background (i.e., only as dark as the background surfaces/props provided behind the displayed character/object).
FIG. 1 illustrates a traditional scrim-based 3D display 100 during its operation to provide a volumetric illusion. As shown, the display 100 includes a physical frame 110 supporting a scrim 120. A foreground platform 130 is shown to extend outward from the frame 110 toward a viewer (not shown) or into the viewing space, which provides additional volume to the display 100. The display 100 includes a backdrop or background set (e.g., a projection surface) 140 as well as physical or real world background objects or props 141, 142 (e.g., 3D objects) between the backdrop 140 and the rear surface of the scrim 120. As shown, operation includes lighting the backdrop 140 (e.g., projecting still or video images onto a projection screen) and also lighting the background props 141, 142 (e.g., with background lighting (not shown) provided behind the frame 110 and scrim 120).
Concurrently, virtual characters 150, 152 are displayed by projecting light from a projector (not shown) onto the front surface or viewer side of the scrim 120. The virtual characters 150, 152 appear to be physically positioned between the foreground props 130 and the background props 141, 142 and backdrop 140. As shown, though, the virtual characters 150, 152 are translucent, which allows lit objects behind the scrim 120 and characters 150, 152 to be seen through the displayed characters (e.g., portions of background props 141, 142 are seen through characters 150, 152). This is undesirable as it ruins the illusion that the characters 150, 152 are solid or real objects. As will be appreciated, projection onto scrims also will not allow the virtual characters to cast a true shadow. For example, the displayed characters 150, 152 in the display 100 do not cast shadows on the background props 141, 142 or onto backdrop/surface 140 as would be expected if the characters 150, 152 were real or physical objects in a scene.
Projection onto scrims also suffers from projector spill onto backgrounds or blow-by. Since a scrim is configured with an open weave to appear transparent or go unnoticed by viewers in areas where it is not projected on and when it is not in use to show virtual characters, significant amounts of projected light pass through the scrim from the foreground space into the background space. As a result, the projected character not only appears on the scrim but also as a double image on background props and surfaces. Hence, the semi-transparency, low-contrast, and lack of shadow aspects of scrim-based displays can spoil the illusion of a solid virtual character integrated into the scene. Projector spill and the need to position the virtual character against a darker portion of the background space limits the character, animation, and set design. Although the use of a beam splitter in a Pepper's Ghost illusion does not suffer from image spilling onto the background, the beam splitter being angled at 45 degrees to the viewer makes the display assembly quite bulky, which has led to it only being used in settings where space is not a significant limitation.
Some attempts have been made to try to address these problems associated with the use of scrims in 3D displays, but these have not been wholly satisfactory to display designers. For example, one typical approach for addressing the fact that the displayed character on the scrim appears semi-transparent has been to choose characters and images for projection on the scrim made up of very bright and light colors and to avoid darker colors. The bright light from the projected character is used to try to overwhelm the background light. However, this leads to a low contrast and an “over-exposed” appearance of the displayed character on the scrim, and it also severely limits character design in such 3D displays.
Another approach, which may be used in conjunction with the above approach, is to make the background very dark in color and with low lighting levels. This approach is used to try to reduce the background bleeding through or being visible through character or other images being displayed on the scrim. Unfortunately, such an approach leads to constrained, dark, and uninteresting backgrounds for scrim-based displays and significantly limits set design (e.g., eliminates many desirable background props and lighting effects in the background space). In other cases, the display is designed such that the background surfaces and/or background props are positioned so as to be relatively far away from the scrim or the projection is angled steeply. This acts to limit blow-by of light as the projector spill tends to land in portions of the background space that cannot be seen by the audience or viewers through the scrim, but, of course, this also limits display or set design and is only useful when the display can be quite large (i.e., not compact).
Due to the shortcomings of such scrim-based displays and Pepper's Ghost displays with beam splitters, there remains a need for systems and methods for providing 3D or volumetric displays such as Pepper's Ghost displays or illusions without the need for special eye or head wear. Preferably, the systems and methods would provide a transparent or 3D display that can be designed to be more compact while also addressing content semi-transparency, low contrast, and blow-by problems associated with traditional scrim-based displays and Pepper's Ghost displays.